Continuous directional drilling



Novu 10, 1953 J. J. ARPs CONTINUOUS DIRECTIONAL DRILLING Filed Jan. 3, 1949 6 Sheets-Sheet l INVENTOR. QB 'DO M Nov. 10, 1953 Fil ed Jan. 5, 1949 J. J. ARPS CONTINUOUS DiRECTIONAL DRILLING 6 Sheets-Sheet 2 NOV. 10, 1953 J. A s 2,658,284

CONTINUOUS DIRECTIONAL DRILLING Filed Jan. 3, 1949 S SheetS-Sheet s 3 a c rrding Pin 26 c Mu'curg I (b) (a) FIG. 10

I23 Mlrcui'g F IG 1 1 (a) INVENTOR.

ga jww u J. J. ARPS 2,658,284

CONTINUOUS DIRECTIONAL DRILLING 6 Sheets-Sheet 4 INVENTOR.

FIG. 5a

llllllllllllllllllllllllllllll lll lllllllll ||||L Nov. 10, 1953 Filed Jan. :5, 1949 Nov. 10, 1953 J. J; ARPS 2,658,284

CONTINUOUS DIRECTIONAL DRILLING Filed Jan. 3, 1949 6 Sheets-Sheet 6 a T b I C d 7 nt 'un mi i! U L D rec FIG. 9

FIG;13

IN V EN TOR.

Patented Nov. 10, 1953 UNITED STATES PATENT OFFICE 32 Claims.

This invention relates to the drilling of wells and has particular reference to controlled directional drilling designed to guide a drill in a definite direction as is necessary in many cases in order to reach a given objective speedily and with certainty.

In order to effect directional drilling it is the practice to insert within the bore hole a deflecting tool such as a whipstock having a guiding surface at an angle with the axis of the bore hole to direct the driil in the desired direction to reach its objective. Correct orientation of this deflecting tool with respect to the magnetic north is of the highest importance for successful controlled directional drilling and it is one object of this invention to make the positioning of the deflecting tool in the desired direction a simple and effective operation.

It is another object of this invention to provide a signalling arrangement for accurately and rapidly determining the orientation of the deflecting tool.

It is another object of this invention to provide an arrangement for continually and automatically recording the inclination and direction of the bore hole while drilling so that corrective measures can be taken at the proper moment.

Conventional means to orientate the deflecting tool are of different types and all have certain disadvantages, which have been overcome in my invention.

The so-called Drill Stem Orientation Method (U. S. Patent 1,770,224 by Alexander Anderson) measures the angular rotation of each stand of drill pipe, while it is run in the hole by means of a set or" transits, one at the top of the drill pipe stand and one just above the derrick floor. When the deflecting tool is at the desired depth, the algebraic sum of the angular rotations of each stand represents the total rotations of the deflecting tool since it was started in the hole in a known position. From this position the angle necessary to bring the tool into the desired orienting position is determined. This method has serious disadvantages, since drill holes which spiral or frequently change their direction, cause a certain amount of torque in the pipe, which may greatly affect the accurate computation of the direction. Also, the method is cumbersome, requires considerable field work and is therefore slow, while its accuracy relies upon the adjustment of the transit and the accuracy of its graduations. Any errors made in reading or recording the amount of direction or rotation of the pipe are cumulative; also proper sighting is impossible during foggy or rainy weather and there is always the possibility of sighting upon the wrong distant target, particularly at night.

The so-called Indirect Method of Orientation (U. S. Patent 1,806,509 by A. G. H. Straatman) requires the knowledge of the direction and inclination of the drill hole at the point at which deflection is intended. This information is usually obtained from a preliminary survey of the hole. Its principle is based upon establishing the angle between the azimuth of the deflecting tool and the known azimuth of the inclination of the bore hole. This may be accomplished by various means such as by providing a landing seat for the inclinometer which has a groove indicating the azimuth of the deflecting tool and by providing the inclinometer with a lead bottom. In setting the inclinometer on the landing seat, an impression will be left on the lead bottom from which the angle between the azimuth of the deflecting tool and that of the bore hole inclination can be determined. Since the direction of the inclination is known from the preliminary directional survey, the actual position of the deflecting tool at the bottom of the hole can be easily determined from the inclinometer record. This method also has serious disadvantages, which are not inherent of my invention. First, the direction of inclination can only be recorder accurately if the angle of inclination from the vertical is not less than three degrees. With inclination angles less than three degrees, the orientation becomes quite inaccurate and in vertical holes the method is useless. Also, while the inclinometer is being run in and out of the hole mud circulation cannot be maintained which may be a serious hazard in caving formations, since the deflecting tool or the drill string may become stuck when the mud circulation is interrupted for some length of time.

The so-called Direct Method of Orientation (U. S. Patent 2,120,670 by Robert Hyer) uses a non-magnetic sub, made out of forged K-Monel metal, which sub contains two small magnets and provisions for seating a directional single shot instrument in which the inclination unit has been replaced by a second compass unt.

The relative azimuth positions between the direction of the deflecting tool and the north attracting magnet in the sub is determined prior to lowering the assembly into the Well. When the deflecting tool has been run to bottom, but prior to setting it, a single shot record is made, which shows both the position of the compass between the predispositioned magnets in the sub and the position of another compass, located in the non-magnetic sub sumciently removed to show the true magnetic north. The actual position of the deflecting tool underground is then computed through a direct reading of the angle between the two compass records.

Another direct method of orientation is the one invented by Bremner and Potter (U. S. Patent No. 2,207,505) which also uses a non-magnetic sub, but has means within this sub to force the inclinometer instrument to rotate and seat in a fixed position in this sub. The disadvantage of both these direct methods of orientation is obvious when it is considered that drilling mud circulation cannot be maintained while the inclinometer instrument is being run inside the drill pipe on a wire line, while waiting for the inclinometer picture to be taken and while retracting the instrument from the hole. In formations, which have a tendency to cave in, this period of time without mud circulation is very hazardous since the deflecting tool or the drill pipe may become stuck, thereby causing a serious fishing job and possibly the loss of the bore hole.

It is the object of my invention to provide means for direct orientation of the deflecting tool at the bottom of the hole, without time consuming and laborious drill stem orientation, which will work just as well in near vertical holes and which will not endanger the hole and the pipe in case a bad caving condition exists, since normal drilling mud circulation can be maintained through the orientation manipulations.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein are set forth by way of example and illustration certain embodiments of my invention.

In the drawings:

Fig, 1 shows a longitudinal vertical section through the bottom part of the bore hole in which a deflecting tool (whipstock) is being orientated by means of an apparatus, constructed in accordance with this invention.

Fig. 2 is a detailed vertical cross section through the orientation apparatus disposed in the drill pipe assembly above the whipstock, conforming to dashed rectangle in the upper portion of Fig. 1.

Fig. 3 is a schematical horizontal cross section through this orientation apparatus, showing the aiming device and signalling instrument.

Fig. 4 is a schematical section through the top of the bore hole, showing the position of the ionization chamber in the mud stream and the recorder which registers the radioactivity of the outgoing mud.

Fig. 5 shows schematically the lower part of the drill stern and particularly the location of an instrument for measuring the inclination and direction of the bore hole during the drilling process.

Fig. 5a represents the cross sectional view of the drill shown in Fig. 5.

Fig. 6 shows the relative location of the main components of the instrument for measuring the inclination and direction of the borehole during the drilling process.

Fig. 7 shows schematically the main elements of the instrument for measuring the inclination and direction and the circuits connecting said element.

Fig. 8 shows an arrangement positioned on the top of the drill hole for producing the record of the inclination and of the direction of the bore hole.

Fig. 9 shows the voltage applied to the tracer electrode and representing the information to be transmitted to the top of the bore hole.

Fig. 10 illustrates diagrammatically an inclination sensing element in vertical position.

Fig. 11 illustrates diagrammatically an inclination sensing element in inclined position.

Fig. 12 shows the output of a relaxation oscillator having a small load resistance.

Fig. 13 shows the output of a relaxation oscillator having a large load resistance.

The objects of the present invention are realized by measuring the direction of the whipstock at the bottom of the drill hole with respect to the magnetic north and converting the result of this measurement into a series of electric pulses. These pulses are passed between a set of electrodes in contact with the drilling fluid or mud stream, one of which consists of or contains a radioactive material. Since the flowing mud is essentially an electrolyte solution, the electric current electrolytically dissolves a certain amount of the electrode metal during each pulse. As a result of this, the mud stream carries a series of local concentrations of radioactive metal ions, corresponding to the number of electric pulses, to the surface, where they are detected and measured by means of a conventional type ionization chamber or radiation counter similar to the one described in my copending application No. 783,280. This number of pulses or peaks on the recorder is then a direct indication of the position of the whipstock at the bottom of the bore hole, so that this deflecting tool can be reset in the desired position.

Referring now to the drawings and more particularly to Fig. 1 thereof, there is shown an apparatus for deflecting a well bore 6 in accordance with conventional directional drilling practice. The upper part of drill string 2 consists of conventional hollow drill pipe 3, which transmits the rotation of the rotary table at the surface to the drilling bit 4 and also serves as a passage for the rotary drilling mud to the bit. In the drawing of Fig. 1 the drill bit is guided by a removable whipstock 5 of conventional design which forces the drill bit in a predetermined direction, thereby causing the bore hole I to deviate in the desired direction. Instead of a removable whipstock 5, a conventional type knuckle joint or spuddin bit could be used. Between the drill pipe 3 and the removable whipstock 5, the orientation and signalling instrument 6 is mounted in a non-magnetic sub '1 of suitable metal, preferably forged K-Monel, and of a length suflicient to remove the instrument 6 far enough away from the iron of the drill pipe 3 and the deflecting tool 5 in order to record an undisturbed earth magnetic field. A length of around 15 feet for the non-magnetic sub is usually suflicient for this purpose. Rotary mud, pumped from the surface in a conventional manner passes through the hollow drill string 3, through non-magnetic sub 7, around orientation signalling unit 6 to the orifices 8 of drill bit 4 and from there upward through the annular space between bore hole I and drill string 3 to the surface.

Referrin now more particularly to the surface arrangement of Fig. 4, it will be noted that the mud emerging between the drill string 2 and the surface casing 9 passes through flowline l0 and around ionization chamber I l to the conventional mud ditch Ha and mud suction pit, from where it is picked up by the mud pumps to be recirculated down the hole through the drill string. The ionization chamber is of a conventional type filled with gas such as argon at superatmospheric pressure and has its terminals connected to a circuit comprising a battery M in series with a resistor 4 I a. The voltage across the terminals of the resistor lla represents at any instant the radioactivity of the mud in the immediate neighborhood of the ionization chamber. This voltage is transmitted through the amplifier 42 and applied to a clock driven recorder 43.

It is apparent that each concentration of radioactivity in the mud stream passing in the immediate neighborhood of the ionization chamber causes a corresponding pulse in the recorder 43, and a succession of concentrations produces a succession of pulses as shown by numeral 44.

Consider now Figs. 2 and 3 showing more in detail a portion of the equipment which is enclosed in Fig. 1 within the dashed rectangle l2 and which comprises part of the non-magnetic sub 7 and the orientation signalling unit 6. The orientation signalling unit 6 is composed of a non-magnetic tube l3 which is held in a fixed and predetermined position in the sub with wings l4 secured in slots l5. The unit is held in place by means of a threaded disc l6, which is perforated with holes I! to allow passage of the mud fluid. The top of unit 5 is provided with a stuffing box l8, which seals off around plunger 19. This plunger [9 is provided with a rubber piston 20 which fits loosely in the narrow opening 2! of sub 1, allowing for mud fluid to drain out when the assembly is retracted from the hole. When the assembly is run into the hole the mud fluid entering from below will lift the piston 25] upward thereby allowing the mud to enter the drill string 3. Downward motion of piston 26 and plunger I 9 is counter-acted by a coil spring 22.

Inside the orientation unit 6 plunger [9 is at tached to a cylindrical device 23 which is disposed in a manner to allow a conventional magnetic compass 24 free rotation when plunger I9 is in upward or running position, but which freezes the compass 24 when plunger I9 is in the recording or downward position. The compass 24 is disposed over a circular recording dial 25, which is provided with a series of thirty-six recording pins 26, which are located along the periphery ten degrees apart and held in upward position by springs 21. The compass 24 is provided with two balanced downward extensions 28 and 29. The one attached to the north pole of the magnet 29 is located in such a way that it will push a corresponding recording pin 26 downward when the plunger l9, disc 23, and compass 24 are moved downward, while the extension 23 near the south pole of the magnet is located closer to the center support of the magnet and will therefore not contact any of the recording pins 26. The cylindrical device 23 is equipped near its lower end with a lip type extensions 33 which holds the clock driven rotating arm 3| in place, when plunger I9 is in running or upward position. This rotating arm 3| when released by lip 30 is driven by clock mechanism 32 at a speed of about one complete revolution every thirty-six minutes. Arm 3! is also provided with a sliding electrical contact 31 which touches a series of thirty-six recording contacts 33 disposed at the underside of recording dial 25. These contacts 33 are aligned in a circle, degrees apart and corresponding to the recording pins 26.

The cylindrical device 23 is further equipped with an extension 34 which will close electrical switch 35, when plunger I9 is in downward or recording position. The lower section of the recording signalling unit 6 is provided With a source of electric current such as battery 36. The positive terminal of battery 36 is connected through electric switch 35, recording contact 33, and sliding contact 37 to a button type radioactive electrode 3B which is mounted in a proper insulating material 39 such as rubber or Bakelite in the wall of unit 6 in such a manner that the electrode metal is in contact with the downward flowi mud on the outside. The negative terminal of battery 36 is grounded to the metal of the unit. All metal parts of unit 6, except the magnetic compass 24, are made out of copper, K-Monel or other non-magnetic material.

Operation of the device is as follows: The defleeting tool 5, drilling bit 4, and the orientation device 6 in non-magnetic sub I are run in the hole on drill pipe 3 until the assembly is at the point where directional deviation of the bore hole is desired. The orientation device 6 has previously been orientated with respect to the direction of the deflecting tool 5. The magnetic compass 24 inside unit 6 will turn freely until the north pole is pointing towards the magnetic north. Movement of the compass at this point is unhampered by the freezing device 23, since plunger i3 is in the upward or running position. Also, no current is flowing through the electrical circuit since switch 35 is in open position and rotating arm 3| is locked in zero position by lip extension 36. The position of the recording instrument at this point is more conveniently illustrated in Fig. 3 which shows a schematical horizontal cross section through the orientation instrument along the line A-A of Fig. 2. It will be assumed that the magnetic compass 24 is in a position pointing ninety degrees in a clockwise direction with respect to the whipstock direction indicated by arrow 40. In other Words, the true whipstock direction is ninety degrees west of the magnetic north, and magnetic compass 2d is hovering over the ninth recording pin 26. At this point the mud pumps at the surface are started and the pressure of the downward mud flow forces piston 26 and plunger l9 downward through stufiing box 18 against spring 22. This downward motion of plunger I9 will move cylindrical freezing device 23 downward inside the tubular shell of unit 6. This downward movement of number 23 locks or freezes the magnetic compass 24 in place, and also pushes the ninth recording pin 26 downward through recording dial 25 against the small spring 27. At the same time the lip type extension of cylinder 23 unlocks the rotating arm 3|, while extension 343 activates the electrical circuit by means of electrical switch 35. The electrical current from battery 36 now passes from the positive terminal through the recording contact 33, sliding contact 37 mounted on arm 3| to the radioactive electrode 38. From this electrode the current passes through the flowing rotary drilling mud (which is always electrically conductive), back to the metal wall of unit 6 of which the negative battery terminal is grounded. When the current passes from the electrode 38 into the mud, a galvanic dissolving action takes place and a certain amount of metal is dissolved from this electrode into the mud stream in accordance with Faradays law. When, for instance, a radioactive substance such as cadmium is used as electrode material, or included in the electrode material, positively charged cadmium ions will be released from this electrode into the mud stream. Since this isotope of cadmium is an unstable radioactive substance with a half-life of 43 days, it will slowly disintegrate while emitting a 1.5 m. e. v. beta radiation and a 0.5 m. .e. v. gamma radiation. The dissolving of the radioactive substance into the drilling mud, in this manner, will make the mud locally radioactive in the portion of the mud stream passing the electrode at the time of such dissolution and this radioactive portion of the mud stream can be easily detected and recorded upon its arrival at the surface. A number .of other radioactive substances are suitable for this purpose, some of which are more fully described in my abovementioned co-pending application Serial No. 783,280.

The rotating arm 3| after being released by lip extension 39 is turned slowly by clock mechanism 32 and alternately closes and opens the electrical circuit each time sliding contact 31 comes opposite one of the recording contacts 33. Under the condition shown in Fig. 3 this will occur exactly nine times, after which .the rotating arm 3| will be stopped by the protruding ninth recording pin 26.

In the mud stream there will thus be introduced nine separate local concentrations of radioactive metal tracer. The presence of these concentrations is picked up by ionization chamber l I (Fig. 4) as they are conveyed to the surface in the mud stream and recorded on the clock driven recorder 43as a series of nine equidistant peaks M. The

operator observing this recorder then concludes that the whipstock is positioned nine times ten or ninety degrees counterclockwise from the direction of the magnetic north and can proceed toturn the assembly from the surface in the desired direction over the desired angle. The mud pumps are then stopped and as a result the piston and plunger I9.are pushed back to their original position by spring 22, thereby deactivating the electrical circuit by opening switch 35, releasing the locked recording arm 3| by retraction of recording pin 2?; and unlocking the magnetic compass 24 byraising the disc 23a. The arm 3.! will then rotate back to its starting positional; B and stop.

The unit is now ready for a check run. When sufficient time has elapsed to make arm 3| return to the zero position 13, the mud pumps are started up again and the above described procedure repeated. When the second observation confirms that the whipstock is now in the desired position, the directional drilling operation can proceed directly.

It is thus apparent that I have provided a sys tem for positioning the deflecting tools in the desired direction that is simple and reliable in operation.

Consider nowFigs. 5 to 13 showing an arrangement for continually recording the direction and inclination of the drill hole while drilling is in progress by means of essentially the same system of using the flowing mud stream as a carrier of electrolytically released radioactive signal tracers. Referring to these drawings and moreparticularly to Fig. 5, there :is shown a cross section through the lower part of adrill string, equipped for continuous recording of direction and inclination of the borehole while drilling. The conventional drilling bit 20.9 is attached to drill collar '20! of standard design. Between this drill collar ZEN and the conventional hollow drill pipe 262 is a non-magnetic sub 203, which contains the sensing and signalling equipment for continuous directional drilling in a cylindrical opening 264. This cylindrical space is in an eccentric position with respect to the axis of the non-magnetic sub '203,

8 so as to provide space for the regular mud channel 235, as shown in the horizontal cross section of Fig. 5A.

Consider now Fig. 6, which is a more detailed drawing of the sensing and signalling equipment enclosed by the dashed rectangle 205 of Fig. 5 and shows the mud operated electrical switch .59 and the relative position of the main components of the instruments contained in space 284. Switch 50 is contained in a cylindrical housing positioned in a recess 261 in sub 203. These main components of the arrangement, together with the electrical circuits connecting said components are shown included in dotted lines in Fig. '7 as follows: Mud operated switch 50, current supply 5|, exploring element 52, signal storage element 53, time delay relay H2, translating circuit 54 and electrode system 55. The exploring element 52 comprises an inclinometer 55a and direction meter 56. These components will be described now more in detail.

The mud operated switch 58 designated diagrammatically in Fig. 7 is shown more in detail in Fig. 6. It is essentially a mechanism operated differentially by the difference in mud pressure between the inside of the drill collar and the annulus around it. The switch connections are actuated during two significant periods: (a) when the drilling is temporarily stopped; for instance, when the kelly is removed for adding a new pipe joint to the drill string, and (b) when the drilling is resumed. During the first period the mud circulation stops and the difference in mud pressure operates the switch so as to activate the measuring devices at the bottom of the drill hole. Dur ing the second period the mud circulation is resumed and the change in the mud pressure reverses the switch connections so as to release the result of measurements to the top of the drill hole. Consequently, the desired information regarding the dip and inclination of the hole is automatically and continually released by means of the switch .50 each time the drilling operation is discontinued and subsequently resumed.

The switch 58 consists of a contact element comprising two stationary terminals 65, 66 and a movable terminal 61 having a form of a metal strip the lower portion of which is fixed, and upper portion is attached to the shaft 58. The metal strip is arranged to be moved with the shaft to make a contact either with the terminal 66 or with the terminal 65. The shaft 68 is provided with two stops 69, 10 which limit its motion to the extent necessary to make the contacts. The portion of the shaft between the two stops and the contacts is contained within the cylindrical vessel TI to be protected from the intrusion of drilling fluid. The remaining portion of the shaft 68 protrudes through the stuffing box to a membrane E2. The control of the switch can be described as follows: When the drilling is in progress a stream of mud flows through the circular channel 13 of the drill collar sub, and the differential pressure between the inside of the drill collar and the outside annular space tends to move the membrane '12 in the direction of the arrow 14. The motion of the membrane actuates the shaft 68 thereby breaking the connection between terminals 68,6! and establishing connection between terminals 65,-6'1. When, however, the drilling is temporarily stopped (in order, for instance, to add a new pipe joint), the flow of the mud stops and, consequently, the pressure inside of the drill collar becomes equal to the pressure in the outside annular space. The equalization of these two pressures has an effect to move the membrane 12 in the direction opposite to the arrow 14 thereby moving the shaft cs so as to break the connection between the terminals 65, 91 and to establish connection between the terminals St, E1.

The current supply system comprised within dotted lines i comprises a battery It in series with resistor '51. The resistor ii is relatively large and, therefore, we have a Substantially constant current system. Thev current delivered from the output terminals 18, i9 is substantially independent of the variation of load across said terminals.

The exploring element is shown within a dotted cylinder 52, inclined with respect to vertical, to represent symbolically the dependence of this element upon its attitude relative to the bore hole. The exploring element comprises two components acting independently one of the other: an inclinometer 55a. and a direction meter 56. The inclinometer is an inclination sensitive element comprising a suitable resistor having terminals 80, 8|, the resistance between said terminals being a function of the inclination of said element with respect to the vertical. The direction meter is a direction sensitive element comprising a resistor having terminals 8|, 82 the resistance between said terminals being a function of the direction of said element with respect to the magnetic north. Both the inclinometer and the direction meter are fixedly mounted Within proper openings in the drill collar as shown in Fig. 6 in such a manner that when the drill hole deviates from the vertical position the value of the resistance between the terminals 99, iii changes in response to the inclination of the hole, and the value ofthe resistance between the terminals iii, 82 varies in response to the direction of the hole with respect to the magnetic north.

Assume now that the switch 50 is in the position shown in Fig. 7 at which connection is estab lished between terminals 86, E7 and connection is broken between terminals E5, 61. Such a situation exists when the drilling is temporarily discontinued and the mud circulation stopped. Under such conditions the battery it delivers a constant current through the terminals 18 to terminals 61, 56 into the terminal 80, through the inclinometer 55a, then through the terminal 2| into the direction meter 58, then through the terminal 82 and the terminal is back to the bat tery '16.

Consequently a constant current is flowing through two resistance elements between terminals 80, 3| and 8|, 82, said resistance elements being respectively responsive to the inclination and direction of the bore hole. In particular, the voltage between terminals 89, 3| varies with the inclination of the bore hole and the voltage be tween the terminals 8!, 82 varies with the direction of the hole with respect to the magnetic north. These two voltages contain the information that it is desired to transmit to the top of the drill hole in order to advise the operator regarding the inclination and direction of the hole.

In the arrangement of Fig. 7 the two voltage signals containing the desired information are not immediately transmitted to the top of the drill hole. They are temporarily stored in a suitable storage element 53 and retained there until the drilling is resumed.

The storage element comprises condensers 99, at that are arranged to store voltages representing the direction and inclination of the bore hole, respectively.

The condenser has one of its terminals connected through a resistor 92 and rectifier 93 to the terminal 82 of the direction meter. The other terminal of the condenser 90 is connected directly to the terminal 8|. It is desired here to provide an arrangement allowing the voltage derived from the terminals BI, 32 of the direction meter to charge the condenser 90 and for this purpose the rectifier 93 is provided in order to prevent any discharge.

The condenser 9| has one of its terminals connected through a resistor 94 and rectifier 95 to the terminal 8!] of the inclinometer. The other terminal of the condenser 9| is connected directly to the terminal 8| The rectifier 95 is provided to enable the voltage derived from the inclination meter to charge the condenser 9| and to prevent any discharge.

The output terminals of the condensers 90, 9| are applied to the trans ating circuit 54 which in turn has its output terminals 9'5 and 91a connected to the tracer electrode 98 and to ground 99, respectively. The translating circuit has two sets of control terminals I09 and lei. A voltage applied to the control terminals I00 energizes the translating circuit and initiates its operation. A voltage applied to the control terminals |0| deenergizes the circuit and stops its operation.

We are considering now the period during which the drilling is discontinued and the two signals representing the direction and inclination are applied to and stored in the condensers 99, 9|. During this period no voltage is applied to the control terminals I09, llil. Consequently, the translating circuit is deenergized and the condensers 90, 9| remain continually charged.

When, however, the drilling is resumed the mud circulation starts again and the differential pressure between the inside of the drill collar and the outside annular space moves the metal strip 61 to a position designated by dotted lines in Fig. '7. At this position connection between terminals 65, 61 is broken and connection between terminals 65, 6'! is established. This has as an effect to disconnect the inclinometer 55a and the direction meter 56 from the current supply 5| and to connect the current supply through the channels H0, III to the control terminals |00 and ml, respectively. This can be seen by verifying the connections shown in Fig. '7. The output terminal 19 of the current supply is directly connected to one of the leads of each of the channels I 50, and the output terminal 18 is connected to the other lead of each of the channels I I0, I I I through the contacts 6?, 65 of the switch 50. The channel I i0 is in turn applied directly to the control terminals I00. The channel I is connected to the input of a suitable time delay relay H2, the output which is connected through the leads H3 to the control terminals |0|. Consequently, as soon as the switch 50 establishes contact between the terminals 65, 61 a voltage is delivered by the current supply 5| through the channel I I0 to the control terminals I00 and energizes the translating circuit. At the same instant the same voltage is applied through leads I to the input of the relay H2. The relay is of a delay type and is arranged to transmit the applied voltage after a time delay of T seconds through the leads H3 to the control terminals |0|. This delayed voltage deenergizes the translating circuit.

It is thus apparent that as soon as contact is established between terminals 65, 61 the translating circuit 54 is arranged to become operative for a time interval of T seconds.

The translating circuit is adapted to receive voltages derived from condensers 90, 9| and to produce across the output terminals 91 and 91a in response to these voltages a succession of pulses a, b, c, d, etc. as shown in Fig. 9. The pulse a has a duration of di seconds and the interval between this pulse and the succeeding pulse b has a duration of dz seconds.

The value d1 is arranged to be equal to the magnitude of the voltage across the condenser 90 (representing the direction of the hole) and the value dz is arranged to be equal to the voltage across the condenser 9| (representing the inclination of the hole). The succeeding voltages c, d do not carry any additional information and it is desired to eliminate them from the output of the translating circuit. It is noted that the first two pulses a, b take place within the initial period of T seconds and, therefore, in order to eliminate the succeeding pulses a provision has been made to maintain the translating circuit in operative condition only during the period of T seconds. This is efiected by means of control voltages applied to terminals I00 and IN, respectively. At the instant at which it is desired to transmit the two significant signals (temporarily retained by the storage element 53) into the translating circuit 54 a voltage is applied to the control terminals [00. This has an efiect to initiate the operation of the translating circuit.

After an interval of T seconds another voltage is applied to the control terminals 101 and has as an effect to render the translating circuit inoperative.

It is thus apparent that the total process covered by this invention takes place in two succeeding time intervals. During the first time interval when the drilling is temporarily discontinued and the mud circulation stops the movable terminal 61 of the switch 50 is in contact with the terminal 56 and the two signals carrying inclination and direction of the hole are temporarily retained in the storage element 53. During the next time interval the drilling is resumed, the mud circulation starts which in turn actuates the switch 50 by opening the contact between the terminals 61, 66 and simultaneously closing the contact between the terminals 61, 65. The action of the switch 50 initiates the release of the two signals from the storage element 53 through the translating circuit 54. We obtain thus across the output terminals 91 and 91a of the translating circuit two pulses such as a and 1) shown in Fig. 9. The width (11 of the pulse 11 represents the direction of the bore hole and the width dz separating the two pulses represents the inclination.

The output terminals 91 and 91a of the translating circuit are applied to ground 99 and to a tracer electrode 38. The tracer electrode is made of or contains a suitable radioactive substance as hereinbcfore mentioned and as described more fully in my copending application Serial No. 783,280. Consequently, the two current impulses as shown in Fig. 9 when applied to the tracer electrode 98 will release into the mud a suitable amount of radioactive substance. It is apparent that when the impulse a is applied to the tracer electrode we obtain a continuous release of the radioactive substance into the mud as long as the pulse continues. The radioactive substance is then carried by the mud stream to the earths surface and subsequently detected by means of an ionization chamber l l (Fig. 8) by means of which we obtain an electrical current as long as radioactive tracer is present 'inthe output stream of drilling mud. When the voltage pulse applied to the electrode decays to zero, the dissolution of the radioactive tracer into the mud stream ceases and (after a suitable time suincient to carry the tracer to the top of the hole) the output of the ionization chamber l l decays to zero. We obtain thus across the output of the ionization chamber a current pulse the duration of which represents the current pulse applied to the electrode.

Consequently, the two pulses of Fig. 9 applied to the tracer electrode 93 produce (after a suitable time interval required for the travel of mud) two corresponding pulses in the output of the ionization chamber H. These two pulses are recorded by means of an appropriate arrangement shown in Fig. 8. It is apparent that the length of the recorded pulse (11 represents the direction of the hole, and the time interval dz between these two pulses represents the inclination of the hole.

It is thus apparent that I have provided a method and means for transmitting to the driller information regarding the direction and inclination of the bore hole during drilling.

Consider now the structural characteristics of the inclinometer 5511. As shown in Fig. 7, the inclinometer comprises a hollow Bakelite cylinder I28. The cylinder is provided with two metallic discs !2 l, I22 covering its top and bottom, respectively, so as to form a sealed container. The discs are electrically connected one to the other by means of a series of elongated resistor elements 23 disposed longitudinally with respect to the axis along the internal wall of the cylinder. The resistance of each of these elements is not uniform throughout its length, namely its lower half has a smaller cross section and therefore ofiers higher resistance to the current. The cylinder container is filled with mercury which occupies the lower half of its volume. When the cylinder is in vertical position as shown schematically in Fig. 10a, all the lower portions of the resistors l23 are submerged and therefore offer practically no contribution to the total resistance between the terminals 86, 8|, the only contribution being due to the upper portion. Therefore the actual resistance between the terminals 83, 8! as schematically shown in Fig. 10b consists of the plurality of upper portions of resistors !23 in parallel. Since these portions of resistors I23 have a relatively large cross section the total resistance between the terminals 80, 8! is small.

When the cylinder is in tilted position as shown in Fig. 11a some of the small cross section resistors are not submerged by the mercury and therefore short circuited. Consequently, the actual resistance between the terminals 89, 8| as schematically shown in Fig. 11b is larger than in Fig. 102).

It is thus apparent that the resistance between the terminals 539, 8! is responsive to the inclination of the cylindrical element and it increases with the increase of the inclination.

Consider now the directional meter 58. It comprises two main components: an earth magnet !25 and a toroidal element I25. The magnet is secured on a rotatable shaft (27, said shaft being' held in coaxial position by end bearings I28, [28. The element I26 comprises a toroidally wound wire resistance element having a discontinuity at l25a. This resistance element is supported for rotation with shaft i2! by means of a rigid, electrically conductive arm I30 which makes electrical connection at its upper end with one end of the resistance wire element at the V ductive.

before-mentioned point of discontinuity. Arm I30 thus serves to make electrical connection from the resistance element I26 to the terminal 82. Within the toroidal element is positioned a metal disc I3I supported by rod I32 in such a manner as not to make electrical contacts with the winding of the toroidal resistor. A steel ball I33 is resting on the periphery of the metal disc inside of the toroidal element, thereby providing an electrical connection between said disc and a point on the toroidal resistor winding representing a direction diametrically opposite from the direction of inclination of the instrument.

It is apparent from the inspection of the arrangement shown in Fig. 7 that the current flows i from the terminal 8! to the metal disc I3! then through the steel ball I33 and traverses the portion of the toroidal resistor between the steel ball and the point of connection of conductor arm I30 to return to the other terminal 32. The resistance offered by the toroidal element varies with the position of the discontinuity I26a with respect to the steel ball I33 which in turn is determined by the orientation. of the magnet I25 with respect to the direction of inclination of the instrument. Consequently, the resistance between the terminals 8| 82 varies with the direction of inclination of the instrument with respect to magnetic north.

Consider now the translating circuit 54. The circuit is provided with a pair of input terminals I5I, I52, another pair of input terminals !52, I53, two pairs of control terminals I and. Hit, respectively, and a pair of output terminals 91 and 91a. At the instant a voltage derived from the current supply I is applied through leads I I0 to the input terminals H30 the translating circuit becomes energized. The input terminals I5I, I52 transmit into the circuit the voltage derived from the condenser 30, said voltage representing the direction of the bore hole and the input terminals I52, I53 simultaneously transmit into the circuit the voltage derived from the condenser 9|, said voltage representing the inclination of the bore hole. the translating circuit delivers across the output terminals 91 and 91a two pulses such as shown as a and b in Fig. 9, The width d1 of the pulse a represents the voltage applied across the input terminals I5 I, I52 and the width (12 separating the two pulses represents the voltage applied across the terminals I 52, I 53. After an interval T seconds from the instant of energizaticn of the circuit another controlling voltage is derived from the current supply through. the leads III, time delay network II2 and leads I I3 to the other control terminals IOI. This voltage deenergizes the translating circuit and stops its operation.

The translating circuit 5 comprises a relaxation oscillator of conventional type comprising a gas filled triode I55, storage condenser I56 and a battery I51. The battery is adapted to charge the condenser I56 through resistor I58. After the voltage across the condenser I56 has attained a predetermined value the charging process is discontinued, the gas filled tube I55 which initially was nonconductive becomes automatically con- Consequently, the condenser I55 discharges through the gas filled tube and a triode I 60 in series with the gas filled tube. The triode I60 acts as a resistance element the value of which can be controlled by means of the voltage applied between the grid and the cathode of the triode, said voltage being derived from the input terminals I52, I53. The time interval required In response to these two input voltages,

for the discharge of the condenser I56 across the gas filled tube I 55 and the triode I60 depends upon the effective resistance of the triode. After such a discharge is completed, the gas filled tube I55 becomes again non-conductive and the battery I51 charges again the condenser I56 through the resistor I58. Then, after the condenser I56 has accumulated enough charge, the tube I55 becomes conductive, and the condenser I56 discharges through the tube I55 in series with the triode I60, etc. It is thus seen that the process of charging the condenser I56 and subsequently discharging is recurrent and produces oscillations well known in the art as relaxation oscillations.

The frequency of relaxation oscillations is controlled in a well known manner by the voltage applied between the grid and cathode of the gas filled tube I55, said voltage being derived from the input terminals I 5i, I52. It is apparent that the value of the plate resistance of the triode I 60 controls the discharge time of the relaxation oscillator. Thus Fig. 12 shows the wave shape of the voltage at condenser I56 when the voltage applied across the terminals I52, I53 is zero, and Fig. 13 shows the wave shape of the voltage at condenser I56 when the voltage applied across the terminals I52, I53 is 10 volts.

The action of the voltage derived from the terminals I5I, I52 in determining the frequency of oscillations in effect determines the charge time of condenser I56 and the action of the voltage derived from the terminals I52, I53 in effect determines the discharge time of the condenser. The voltage developed across the triode I60 is applied to a grid of another triode I10'which acts as a non-linear (saturable) resistance in series with resistances HI and I12. The voltage developed across the resistance I12 and applied to the output terminals 91 and 91a will be substantially as shown in Fig. 9. The ground connections schematically illustrated in the translating circuit diagram within the dotted enclosure 54 are not common to the ground connection 99 in the dotted enclosure 55.

It is noted that the plate circuit of the triode I10 is supplied by the battery I13 in series with the switch I14. The switch I14 comprises a stationary terminal I15 and a movable terminal I16, said movable terminal I16 consisting of a. permanently magnetized steel bar adapted to be actuated by solenoids I11 and I18. When a control voltage is applied to the terminals I the solenoid I11 becomes energized and attracts the bar I16 thus closing the switch and rendering the translating circuit operative. If, however, after a period of T seconds another control voltage is applied to the terminals Hill, the solenoid I18 becomes energized. The solenoid I18 has a larger number of turns than the solenoid I11. Consequently, it exerts an attraction on the bar I16 that is stronger than the attraction of the solenoid I11. Therefore, as a result of the application of voltage to the terminals IUI the switch I10 disconnects the current supply to the triode I10 and the translating circuit 54 becomes deenergized.

What is claimed is:

l. The method of determining direction and/0r inclination of a bore hole in the earths crust, which comprises flowing a stream of carrier fluid from a predetermined subsurface point in said bore hole to the top of said bore hole, releasing into said stream at said predetermined subsurface point a detectable tracer substance in a'quantity varying in a manner responsive to and representative of said direction and/or of inclination, and detecting and determining the manner of occurrence of variations in quantity of tracer substance in said stream of carrier fluid arriving at the top of said bore hole to obtain an indication therefrom representative of said direction and/or inclination.

2. The method of determining direction and/or inclination of a bore hole in the earths crust, which comprises flowing a stream of carrier fluid from a "predetermined subsurface point in said bore hole to the top of said bore hole, releasing into said fluid stream at said predetermined subsurface point a radioactive tracer in a quantity representative of said direction and/or inclination, and measuring the quantity of said radioactive tracer at the top of said bore hole to obtain an indication representative of said direction and/or inclination.

3. The method of determining direction and/or inclination of a bore hole containing a carrier fluid, comprising generating an electric current at a determined depth within the bore hole, Varying the character of said electric current as a function of changes in said direction and/or inclination, introducing at said depth into said fluid a selected tracer substance in quantities having definite relation to variation in said current, said quantities being a function of said physical direction and/or inclination, transmitting said carrier fluid to the earths surface, and measuring the quantities of tracer substance in the fluid thus transmitted to the earths surface to obtain an indication representing said direction and/or inclination.

4. The method of determining direction and/or inclination of a bore hole containing a carrier fluid, comprising generating an electric current at a determined depth within the bore hole, varying the character of said electric current as a function of changes of said direction and/or inclination, impressing said electric current upon a pair of spaced electrodes in contact with the conductive fluid in said bore hole, one of said electrodes comprising a suitable tracer substance whereby varying quantities of said substance are introduced into the fluid by said current, said quantities being a function of said direction and/ or inclination, transmitting said carrier fluid to the earths surface, and measuring the quantities of tracer substance thus transmitted in the fluid to the earths surface to obtain an indication representing said direction and/or inclination.

5. The method of determining direction and/or inclination of a bore hole containing a carrier fluid, comprising generating an electric current at a determined depth within the bore hole, varying the character of said electric current as a function of changes of said direction and/or inclination, impressing said electric current upon a pair of spaced electrodes in contact with the conductive fluid in said bore hole, one of said electrodes comprising a radioactive substance whereby a varying quantity of ions of said substance are introduced into the fluid by said current, said quantity being representative of said direction and/or inclination, transmitting said carrier fluid to the earths surface, and measuring the radiations emitted by the ions transmitted to the earths surface in said fluid to obtain an indication representing said direction and/or inclination.

6. The method of determining direction and/ or inclination of a drill hole at a determined depth during a well drilling operation, wherein a circulating fluid is employed to elevate drill cuttings to the earths surface, which comprises generating at said depth a varying electrical current representing said direction and/or inclination and employing said current to release into said fluid a tracer substance in varying quantity representing the variation of said current, said substance traveling with said circulating fluid from said determined depth to the earths surface, and measuring at the earths surface the varying quantity of said substance thus transmitted, said varying quantity thus measured representing said direction and/or inclination.

7. The method of determining direction and/or inclination of a drill hole at a determined depth during a well drilling operation, wherein a circulating fluid employed to elevate drill cuttings to the earths surface, which comprises generating at said depth a varying electrical charge representing said direction and/or inclination and employing said charge electrolytically to release into said fluid corresponding quantities of ions of a tracer substance which serve as carriers of said charge and traveling with said circulating fluid from said determined depth to the earths surface, and measuring at the earths surface the quantities of said substance thus transmitted to obtain an indication representing said direction and/or inclination.

8. The method of determining direction and/or inclination of a drill hole at a determined depth during a well drilling operation, wherein a circulating fluid is employed to elevate drill cuttings to the earths surface, which comprises generating at said depth a varying electrical charge representing said direction and/or in clination and employing said charge to release into said fluid corresponding quantities of radio active ions which serve as carriers of said charge and travel with said circulating fluid from said determined depth to the earths surface, and measuring at the earths surface the radiations emitted by said ions to obtain an indication representing said direction and/or inclination.

9. An arrangement for measuring the inclination of the bore hole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, comprising an exploring means adapted to be lowered to said depth, said exploring means comprising an inclination sensing element for producing an output voltage representing the inclination of the bore hole and an electrode system comprising a radioactive substance in contact with said drilling fluid and responsive to said voltage for electrolytically releasing quantities of said substance into said circulating stream in accordance with said voltage, thereby causing said substance to be carried by said circulating stream to the earths surface, a detector at the earths surface adapted to respond to said radioactivity to produce a signal varying in ac cordance with said quantities of said substance, and a means for indicating said signal.

10. In a rotary drilling system for drilling a bore hole and utilizing a circulating stream of drilling fluid, an arrangement for measuring at a given depth the inclination of said hole with respect to vertical and its direction of inclination with respect to north, comprising an exploring means adapted to be lowered to said depth and of an indicating means at the earths surface, said exploring means comprising a sensing element jointly responsive to the inclination and direction of inclination of said hole for producing a signal representing said inclination and direction and an electrode system comprising a radioactive substance in contact with said drilling fluid and responsive to said signal for electrolytically releasing quantities of said substance into said stream in accordance with said signal, thereby causing said substance to be carried by said circulating stream to the earths surface, said indicating means comprising a detector adapted to respond to radioactivity of said substance to produce a signal representing said inclination and direction and an indicator for indicating said signal.

11. In apparatus for determining the azimuthal direction of a device in a borehole the combination comprising: a body member adapted to be attached to said device; an azimuthal direction sensing means within said body member; a rotary switch including a plurality of contact points and a switch arm carrying a contactor surface rotatable from a predetermined initial position relative to the said body member into successive electrical contacts with said contact points, said contact points being of such size and spacing relative to the dimensions of the said contactor surface as to result thereby in successive intermittent electrical contacts separated by intermediate intervals of non-contact between said contactor surface and said contact points as the arm is rotated; drive means to rotate said arm at a substantially constant rate; means to initiate rotation of said arm from said predetermined initial position, by said drive means; stop means to stop the thus initiated rotation of said arm; means actuated by said direction sensing means to control said stop means to stop the rotation of said arm after having been rotated into contact with a number of said contact points indicative of the azimuthal directional orientation of said body member relative to that of said direction sensing means; and conductors making electrical connection respectively to said switch arm and to said contact points in parallel.

12. Apparatus according to claim 11 in which the said body member comprises a lower portion of a drill stem and in which said means to initiate said rotation of said arm from said predetermined initial position comprises a clutch mechanism actuated by variation in rate of circulation of drilling fluid through said drill stem.

13. Apparatus according to claim 11 and a series electrical circuit connected between said conductors comprising a current source; and a pair of spaced electrodes connected thereto and adapted to make electrical contact with fluid in a borehole surrounding said body members whereby the potential difference between said electrodes is controlled by movement of said switch arm into contact with said contact points.

14. Apparatus according to claim 11, and a pair of spaced-apart electrodes adapted to make electrical contact with fluid in a borehole surrounding said body, at least one of said electrodes comprising a radioactive substance capable of being electrolytically released into such drilling fluid; and means electrically connected to said conductors and controlled by said rotary switch for applying a potential difference between said electrodes which varies in accordance with said successive intermittent electrical contacts between said contactor surface and said contact points of said rotary switch.

15. Apparatus according to claim 13 in which 18 at least one of said electrodes comprises a radioactive substance capable of being electrolytically released into such drilling fluid.

16. In an arrangement for measuring the inclination and/or direction of a borehole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, the combination of an exploring means adapted to be lowered to said depth, said exploring means comprising an inclination sensing element for producing a signal representing the inclination of the borehole; a tracer substance; and a releasing means adapted to release said substance into said circulating stream in accordance with said signal, thereby causing said substance to be carried by said circulating stream to the earths surface.

17. In an arrangement for measuring the inclination and/or direction of a borehole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, the combination of: an exploring means adapted to be lowered to said depth, said exploring means comprising a sensing element for producing a signal representin the direction of inclination of the borehole; a tracer substance; and a releasing means adapted to release said substance into said circulating stream in accordance with said signal, thereby causing said substance to be carried by said circulating stream to the earths surface.

18. In an arrangement for measuring the inclination and/0r direction of a borehole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, the combination of: an exploring means adapted to be lowered to said depth, said exploring means comprising an inclination sensing element for producing a signal representing the inclination of the borehole; a tracer substance; a releasing means adapted to release said substance into said circulating stream in a quantity varying in accordance with a predetermined function of said signal, thereby causing said substance to be carried by said circulating stream to the earths surface in correspondingly varying quantity; means adjacent the earths surface to detect said substance arriving in said circulating stream and to produce in response thereto a second signal varying in accordance with the said varying quantity of said substance therein; and means for indicating said second signal.

19. In an arrangement for measuring the inclination and/or direction of a borehole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, the combination of: an exploring means adapted to be lowered to said depth, said exploring means comprising a sensing element for producing a signal representing the direction of inclination of the borehole; a tracer substance; a releasing means adapted to release said substance into said circulating stream in a quantity varying in accordance with said signal, thereby causing said substance to be carried by said circulating stream to the earths surface in correspondingly varying quantity; means adjacent the earths surface to detect said substance arriving in said circulating stream and to produce in response thereto a second signal varying in accordance with the said varying quantity of said substance; and means for indicating said second signal.

20. In an arrangement for measuring the ingees- 84 I9 clination and/or direction of a borehole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, the combination of: an exploring means adapted to be lowered to said depth, said exploring means comprising sensing means for producing separate output voltages respectively representing the inclination and direction of the borehole; and an electrode system comprising a tracer substance in contact with w said drilling fluid and responsive to said voltages for electrolytically releasing quantities of said substance into said circulating stream varying in accordance with a predetermined function of said voltages, thereby causing said substance to i be carried by said circulating stream to the earths surface.

21. In an arrangement for measuring the inclination and/or direction of a borehole at a given depth adapted to be used in conjunction g with a rotary drilling system utilizing a circulating stream of drilling fluid the combination of: an exploring means adapted to be lowered to said depth, said exploring means comprising sensing means for producing output voltages respectively representing the inclination and direction of the borehole; an electrode system comprising a tracer substance in contact with said drilling fluid and responsive to said voltages for electrolytically releasing quantities of said substance into said circulating stream varying in accordance with a predetermined function of said voltages, thereby causing said substance to be carried by said circulating stream to the earths surface in correspondingly varying quantity; means adjacent the earths surface to detect said substance in said circulating stream and to produce in response thereto a signal varying in accordance with the said varying quantity of said substance; and means for indicating said signal.

22. The method of determining the direction of a borehole in the earths crust, which comprises flowing a stream of carrier fluid from a predetermined subsurface point in said borehole to the top of said borehole, releasing into said stream 1 at said predetermined subsurface point a detectable tracer substance varying in quantity in a manner representative of said direction, and detecting and determining the manner of occurrence of said tracer substance in said stream of carrier fluid arriving at the top of said borehole to obtain therefrom an indication representative of said borehole direction.

23. An arrangement for measuring the direction of a borehole at a given depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, comprising an exploring means adapted to be lowered to said depth, said exploring means comprising a direction sensing element for producing an output voltage representing the direction of the borehole and an electrode system comprising a substance in contact with said drilling fluid and responsive to said voltage for electrically releasing quantities of said substance into said circulating stream varying in a manner bearing a predetermined relation to said voltage, thereby causing said substance to be carried by said circulating stream to the earths surface, and means at the earths surface responsive to the amount of said substance arriving in said circulating stream for producing a signal representative of the manner of variation of said quantities of said substance and thereby obtaining an indication representative of said direction.

24. An arrangement for measu'ringthe inclination of a borehole ata given-depth adapted to be used in conjunction with a rotary drilling system utilizing a circulating stream of drilling fluid, comprising an exploring means adapted to be lowered to said depth, said exploring means comprising an inclination sensing element for producing an output voltage representing the inclination of the borehole and an electrode system comprising a substance in contact with said drilling fluid and responsive to said voltage for electrically releasing quantities of said substance into said circulating stream varying in-a manner bearing a predetermined relation to said voltage, thereby causing said substance to be carried by said circulating stream to the earths surface, and means at the earths surface responsive to the amount of said substance arriving in said circulating stream for producing a signal representative of the manner of variation of said quantities-of said substance and thereby obtaining an indication representative of said inclination.

25. Apparatus according to claim 16 in which said tracer substance comprises radioactive material.

26. Apparatus according to claim 17 in which said tracer substance comprises radioactive material.

27. Apparatus according to claim 18 in which said tracer substance comprises radioactive ma terial.

28. Apparatus according to claim 19 in which said tracer substance comprises radioactive material.

29. An arrangement in accordance with claim 23 in which said substance comprises a radioactive material.

30. An arrangement in accordance with claim 24 in which said substance comprises a radioactive material.

31. Apparatus as defined by claim 16 in which said exploring means includes a circuit having therein a source of electric current and means responsive to rate of flow of the circulating stream of drilling fluid for opening and closing said circuit.

32. Apparatus as defined by claim 23 in which said exploring means includes a circuit having therein a source of electric current and means responsive to rate of flow of the circulating stream of drilling fluid for opening and closing said circuit.

JAN JACOB ARPS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,850,399 Jakosky Mar. 22, 1932 1,963,090 Jakosky June 19, 1934 2,007,465 Burt July 9, 1935 2,010,755 Foley Aug. 6, 1935 2,214,674 Hayward Sept. 10, 1940 2,252,727 Pepper Aug. 19, 1941 2,255,721 Mattingly et a1 Sept. 9, 1941 2,317,259 Doll Apr. 20, 1943 2,329,732 Varney et al Sept. 21, 1943 2,335,409 Hare Nov. 30, 1943 2,341,745 Silverman Feb. 15, 1944 2,380,520 Hassler July 31, 1945 2,425,868 Dillon Aug. 19, 1947 2,453,456 Piety Nov. 9, 1948 

